1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer or a MFP (Multi-Function Peripheral) which is also called a digital composite apparatus.
2. Description of the Related Art
A tandem type image forming apparatus has been known as an image forming apparatus such as a copier or printer. In a tandem type image forming apparatus, plural photosensitive drums are arranged in parallel. Toner images respectively formed on the photosensitive drums are transferred to a paper sheet, and multi-layered on the paper sheet, to obtain a color image. An image forming apparatus of this tandem type has an intermediate transfer belt unit.
Jpn. Pat. Appln. Laid-Open Publication No. 11-237794 describes an example of an image forming apparatus having an intermediate transfer belt unit. In this example, the image forming apparatus has, along with an intermediate transfer belt, a charge removal means for removing electric charges remaining on the intermediate transfer belt. In the charge removal means of this example, a high-resistance material is provided between the transfer belt and a predetermined low-potential part.
Another Jpn. Pat. Appln. Laid-Open Publication No. 2002-72615 also describes an example of an image forming apparatus having an intermediate transfer belt unit. In this example, an electrically charged potential on an intermediate transfer belt is detected after transfer, to control a transfer bias voltage of a toner image.
Still another Jpn. Pat. Appln. Laid-Open Publication No. 2005-308784 describes an example of an image forming apparatus having an intermediate transfer belt unit and a charge removal means for removing electric charges on the intermediate transfer belt. The charge removal means of this example has a bias application means for removing an electrically charged potential from the intermediate transfer belt.
Meanwhile, a primary transfer roller is located facing a photosensitive drum. In order to extend lifecycle of the primary transfer roller, the primary transfer roller is desirably located apart from the photosensitive drum (for example, at color image forming sections during monochrome printing) except for necessary parts.
However, known image forming apparatuses cannot satisfactorily achieve both of improved structural performance of the separation mechanism and guaranteed performance of removing electric charges. Further improvement is demanded.
The present invention provides an image forming apparatus of a tandem type, which is capable of preventing scattering of toner by a charge removal mechanism and extending lifecycle of components.